Conversion of hydrocarbons with fluidized solid particles in the presence of combustion gases containing hydrogen



. W Wm WM 5 14 7 3 5 a "A H v I; M W 1 ||11l| r I 11311.. X W W E U. i 1|i1. I fly l Q 5 WMHim Ha 2 3 7 f M. FIDELMAN CONVERSION OF HYDROCARBONS WITH FLUIDIZED SOLID PARTICLES IN THE PRESENCE OF COMBUSTION GASES CONTAINING HYDROGEN Filed July 1,

May 8, 1962 United States Patent 3,033,779 CONVERSION OF HYDROCARBONS WITH FLUID- IZED SOLID PARTICLES IN THE PRESENCE OF COMBUSTION GASES CONTAINING HY- DROGEN 7 Morris Fidelman, Glen Oaks, N.Y., assignor to Hydrocarbon Research, Inc., New York, N.Y., a corporation of New Jersey Filed July 1, 1953, Ser. No. 365,449 6 Claims. (Cl. 208-127) This invention relates to the high-temperature treatment of hydrocarbons and is more particularly concerned with the efiicient production of high octane gasoline from heavy oils, especially those which have a high content of sulfur, nitrogen or metal compounds.

Various processes have been proposed for converting heavy hydrocarbons to lighter hydrocarbons boiling in the gasoline range and a large proportion of these processes involve the conversion of the hydrocarbons in the presence of particulate contact material on which a carbonaceous deposit is formed by the hydrocarbons undergoing conversion and which is subjected to regeneration to remove the carbonaceous deposit. Generally, the heavier the feed hydrocarbons are, the greater is the amount of carbonaceous deposit formed on the contact material and, consequently, the greater is the problem of regenerating the contact material. Since the cost of re generating the contact material is an important factor in the operating cost of the hydrocarbon conversion process as a whole, it is readily seen that several processes and/ or hydrocarbon stocks cannot be used commercially because of the unfavorable economics of the regeneration step.

A principal object of the invention is to regenerate the contact material by converting the carbonaceous deposit thereon to valuable gaseous products.

Another important object is to utilize a portion of the gaseous products of regeneration in the conversion of the hydrocarbons to improve the yield and quality of the hydrocarbon conversion products.

A further important object is to transport the contact material back to the hydrocarbon conversion zone while simultaneously eilecting the removal of a portion of the carbonaceous deposit thereon.

Additional objects and advantages of the invention will be apparent from the description which follows.

In accordance with the invention, hydrocarbon oil is subjected to treatment at elevated temperatures in the presence of a particulate contact material or carrier and a hydrogen-containing atmosphere produced by the reaction of a controlled quantity of carbon with oxygen and steam at temperatures above about 1600 F. The carbon deposited on the carrier in the hydrocarbon treatmentzone is gasified in two regeneration zones, one of which provides the previously mentioned hydrogen-containing atmosphere. The hydrocarbon conversion zone and the two regeneration zones are arranged in communication with each other so that the solid carrier particles circulate from the conversion zone to the first regeneration zone, thence to the second regeneration zone, and thence back to the conversion zone, while the hydrogen-containing regeneration product gases flow from the first regeneration zone through the conversion zone and a gaseous product eflluent is separately withdrawn from the second regeneration zone.

With the particulate carrier in a fluidized state, the hydrocarbon treatment or conversion zone and the two regeneration zones are preferably arranged in a single vessel with the hydrocarbon treatment zone superposed over the first regeneration zone and with a second regeneration zone parallel to and substantially coextensive with both the conversion and first regeneration zones. A

flow-restricting bafile structure is placed between the conversion and first regeneration zones to permit the maintenance of substantially different temperatures in these zones while allowing the regeneration product gases to ascend from the first regeneration zone into the conversion zone and fouled carrier particles to descend from the conversion zone into the first regeneration zone. The lower end of the second regeneration zone communicateswith the first regeneration zone and its upper end with the conversion zone; carrier particles flowing from the first regeneration zone to the second regeneration zone are conveyed therethrough, while a portion of the carbonaceous deposit on these particles is gasified, to the conversion zone to contact again the hydrocarbons undergoing treatment.

It is generally advisable to interpose a secondary cracking zone between the Cracking and first regeneration zones. type disclosed in the application of Finneran et 21., Serial No. 299,114, filed July 16, 1952, now U.S. Patent No. 2,861,943 wherein fluidization of the particulate carrier is restained in the sense that the vertical movements of the fluidized particles are restricted to the extent that a temperature gradient is established along the vertical dimension of the secondary cracking Zone, ranging from the temperature of the upper cracking zone which is contiguous with the upper end of the secondary cracking zone to the higher temperature of the first regeneration zone which is contiguous with the lower end of the secondary zone. Such restrained fluidization is obtained by filling the secondary cracking zone with coarse packing bodies like Raschig rings and Berl saddles.

Accordingly, in a preferred embodiment of the invention, fluidized carrier particles circulate through a system which includes the primary cracking zone into which the hydrocarbon oil, preferably preheated, is fed. Conversion of the hydrocarbon oil deposits heavy hydrocarbons and carbon on the carrier particles and these particles are passed with restained fluidization downwardly through the secondary cracking zone in countercurrent contact with a stream of regeneration product gases containing hydrogen and formed by reacting carbon with high-purity oxygen and steam at a temperature above about 1600 F. in the first regeneration zone. From the secondary cracking zone, the particulate carrier passes into the first regeneration zone wherein enough of the carbonaceous matter on the carrier is reacted with steam and oxygen to yield the hydrogen-containing product. gases that are required in both the primary and the secondary cracking zones. Besides hydrogen, these regeneration product gases contain carbon monoxide, carbon dioxide and excess steam, and, after passing upwardly through the secondary and primary cracking zones, these gases are withdrawn together with the hydrocarbon conversion products from the top of the primary cracking zone as a single gaseous efiluent. In converting heavy hydrocarbon oils, more carbonaceous matter is deposited on the carrier than can profitably be gasified to provide the desired hydrogen in the cracking zones. If all of the hydrogen-containing regeneration product gases derived from all the carbonaceous matter were passed into the cracking zones, undue dilution of hydrocarbon conversion products in the total gaseous eflluent of the primary crack: ing zone would result, thus unnecessarily increasing the size of the recovery plant required to separate the various products in the total gaseous efiiuent. However, since in accordance with this invention only a portion of the carbon is gasified in the first regeneration zone, the carrier is passed to a second regeneration zone wherein the excess carbonaceous matter is removed by a gasifying reaction and from which the carrier is returned to the primary cracking zone. The gases produced in the second Patented May 8, 1962 Preferably, the secondary cracking zone is of the 3 regeneration zone are withdrawn as a by-product stream which is independent of the production and withdrawal of the total gaseous effluent. Gasifying conditions in the first regeneration zone are therefore set to provide hydrogen-containing gases which are best suited for utilization in the hydrocarbon conversion, regardless of the total amount of carbonaceous matter which must be removed from the carrier particles before the particles are returned to the conversion zone. I

From the total efiluent, a good yield of high octane gasoline is recovered, even when the feed stock is a heavy crude or residual oil containing large quantities of sulfur, nitrogen and metal compounds. This yield of high octane gasoline is obtained with minimum formation of hydrocarbons boiling above the gasoline range (end point of 400 F.), and these higher boiling hydrocarbons may be recycled to the conversion process to form additional gasoline or utilized as feed to a conventional catalytic cracker or sold as fuel.

In most cases, the gasoline produced'by the process of this inventionhas a sulfur content within commercially desirable limits and is in other respects an acceptable product. In those cases where, because of the excessive- 1y poor quality of the oil treated, the gasoline produced, although of much reduced sulfur content, still contains more sulfur than is desirable or has less than the desired stability characteristics, the sulfur content and the stahility characteristics can be brought to acceptable values by known refining processes, e.g., catalytic treatment of the gasoline with hydrogen at elevated temperatures.

The particulate carrier which is employed in the process of the invention is 'any solid heat-resistant material, such as sand, quartz, alumina, magnesia, zircon, beryl, bauxite or other like material, which will withstand the desired regeneration conditions including a temperature above 1600" F. without physically disintegrating or fusing. The entire reaction system, i.e., the primary cracking zone, the secondary cracking zone if present, and the first and second regeneration zones, is generally maintained at a total pressure in the range of about 150 to 800 p.s.i.g. (pounds per square inch gage), preferably 250 to 650 p.s.i.g., while a hydrogen partial pressure of at least 35 psi. (pounds per square inch), preferably 75 to 150 p.s.i., is maintained in the primary and secondary cracking zones by the passage therethrough of the regeneration product gases from the first regeneration zone. A hydrogen partial pressure in excess of 150 p.s.i. is not necessary since maximu'mbenefits from the presence of hydrogen are obtained in the indicated range and there is little or no economic justification for employing a hydro; gen partial pressure above 150 p.s.i. The use of total pressures in the indicated range also providesa high oxygen partial pressure in each regeneration zone, increasing the rate of regeneration and allows eflicient recovery of the normally liquid hydrocarbon products from the total gaseous eflluent.

Y The temperature of the primary cracking zone is maintained in the range of 850 to 1100 F., preferably 900 to 1050 E, by control ofthe temperature and quantity of carrier transferred from the second regeneration zone, and by control of the temperature to which the hydrocarbon oil feed is preheated, The feed rate of hydrocarbon o'il is desirably maintained at 0.2 to 3.0, preferably 0.5 to 1.5, volumes of liquid oil per hour volume ,of the primary cracking zone. The oil partial pressure, determined essentially by the rate of hydrocarbon oil feed and the volume. of regeneration product gases, may vary from about 5 to 100 p.s.i., preferably from to 50 psi. It is a feature of the invention that the preferred range of conversion temperature is higher and the preferred range ofoil partial pressure lower than are generally employed in thermal cracking processes, and as a consequence the gasoline which is produced is considerably higher in octane number than that produced in such processes, approximating 90 OFRR octane number without use of tetra-ethyl lead or other anti-knock additives.

In the first regeneration zone, part of the non-volatile carbonaceous deposit on the particulate carrier is reacted with a regenerating gas consisting essentially of steam and oxygen, at a temperature in the range of 1600 to 2500 F., preferably 1700 to 2000 F. The regenerating gas contains a preponderance of steam and a minor proportion of high-purity oxygen, the latter more specifically containingat least about 90% by volume of oxygen, preferably at least 95% by volume of oxygen, and obtained, for example, by air liquefaction and rectification. Steamto-oxygen volume ratios in the range of 1.5 :1 to 5:1 are generally satisfactory for generating the required quantity of hydrogen. It is preferable, as a practical matter, to employ a steam-to-oxygen volume ratio of the order of 2:1 to 3:1 and thereby avoid a very' high regeneration temperature.

The regeneration of the carrier results in the production of a gaseous mixturecomprising essentially hydrogen, carbon monoxide, carbon dioxide and excess steam. The gaseous mixture from the first regeneration zone passes through the secondarycracking zone, if present, and the primary cracking zone, providing therein the desired hydrogen and acting as the principal medium for carrier fiuidization.

ln 'the second regeneration zone, excessfcarbonaceous matter is removed from the carrier by a gasifying reaction. For instance, any oxygemcontaining gas may be used to convert the carbon to carbon oxides. Preferably, the carbon is gasified to produce valuable gases like hydrogen and carbon monoxide, and for this purpose steam and high-purity oxygen are supplied to the second regen eration zone. While the resulting product gases, rich in hydrogen and carbon monoxide, may be advantageously utilized in various chemical and metallurgical processes, an important use contemplated by this invention is in the refining of the cracked gasoline recovered from the total gaseous efiluent. The refining of cracked gasoline in the presence of hydrogen to eliminate sulfur compounds and gum-forming constituents is illustrated by the process of copending application Serial No. 272,512, filed February 19, 1952, in the names of C. A. Johnson and S. C. Schuman, on which U.S. Patent 2,774,718 was granted December 18, 195-6. Gases rich in hydrogen and car bon monoxide, 'as produced in the second regeneration zone, are well suited for direct utilization in such gasoline refining processes; in some instances, the hydrogen con centration of the product 'ga'ses may profitably be increased prior to using these gases in the refining of gasoline simply by subjecting them to the well known watergas shift reaction:

COz-i-Hz It appears that carbon which is subjected-to gasification in the presence of steam: at temperatures above 1600" F. undergoes activation. Accordingly, it is often desirable to leave of the order of not more than 2% by weight of the activated carbon on the carrier particles returned to the primary cracking zone.

The two regeneration zones provide the process of this invention with considerable operational flexibility. For instance, the first regeneration zone maybe operated with a low steam-to-oxygen ratio, say '2, to increase the hydrogen partial pressure in the regeneration product gases and thus, decrease the volume of the total gaseous eflluent sent to the recovery system; this would tend to raise the regeneration temperature which could be counterbalanced by using a high steam-to-oxygen ratio in the second regeneration zone to lower the temperature of the carrier. p

For a fuller understanding of the invention, reference is made to the accompanying drawings wherein; p

FIGURE 1 is a sectional elevation, represented schematically, of a preferred reactonfor use inaccordance with this invention; a I

FIGURE '2 is a similar view of a modified reactor; and FIGURE 3 is a diagrammatic fiowsheet' of the combination of a reactor such as shown in FIGURE 1 or 2 with a gasoline refining plant which is supplied with hydrogen produced in the secoind regeneration zone of the reactor.

In FIGURE 1, an upright cylindrical vessel is provided with a flow-restricting bafile structure 11 at an intermediate level therein to permit the maintenance of different temperatures in the fluidized carrier particles on opposite sides of bafile structure 11 which is shown as a perforated plate but, as known, may take the form of a grill, a screen or closely spaced bafiie slats. Plate 11, in effect, divides vessel 10 into a first regeneration zone 12 and a cracking zone 13. Since it is preferred to use also a secondary cracking zone, the latter is formed by a bed of packing bodies 14, such as 2-inch Raschig rings, supported by plate 11 and filling the lower portion of zone 13. Thus, the upper unpacked portion of zone 13 becomes primary cracking zone 15 and the bed of Raschig rings 14 provides secondary cracking zone 16. A tube 17 extends from the lower end portion to the upper end portion of vessel 10, passing through plate 11 and the bed of rings 14. An adjustable valve 18 at the bottom of vessel 10 functions to control the flow of fluidized particles into tube 17 and has a tubular stem 19 and openings 20 through which a gaseous stream is injected into tube 17 both to gasify carbonaceous material on the carrier particles and to transport these particles from zone 12 to the top end portion of vessel 10. Tube 17, which may increase in diameter upwardly, is nested at its upper end inside larger tube 21 and forms therewith an annular path 22. To facilitate the separation of gases and solids at the top end of tube 17, it is advisable to enlarge the upper section of tube 21 as shown at 23. Tube section 23 is fastened to the top of vessel 10 and provides a settling chamber for the solids carried up through tube 17 by the up-flowing gases which leave vessel 10 through outlet 24. If desired, a filter or cyclone separator may be placed in tube section 23 so that the gases pass therethrough before exiting through outlet 24. At the bottom of first regeneration zone 12 is an inlet 25 for introducing the regenerating gas. In primary cracking zone 15, there is a feed distributor 26 for introducing the hydrocarbon oil from pipe 27 and an outlet 28 for removing the total gaseous effluent.

In operating the reactor of FIGURE 1, the fluidized mass in zone 15 has a gas-solid interface 29 and that in tube section 23 has interface 30. Carrier particles which become fouled in primary cracking zone 15 move downwardly through secondary cracking zone 16 wherein the temperature increases and u-p-fiowing regeneration product gases rich in hydrogen act to crack and strip off heavy hydrocarbons adsorbed on the fouled carrier particles. Thence, carrier particles with a substantially dry carbonaceous deposit discharge into first regeneration zone 12 in which a portion of the carbonaceous deposit is gasified to produce the hydrogen-rich gases. The regeneration product gases from zone 12 and the hydrocarbon conversion products form the total gaseous efiiuent which emerges from interface 29 and leaves the reactor through outlet 28. Partially regenerated carrier particles flow into the lower end of tube 17 and are conveyed upwardly by regenerating gas entering by Way of openings 20 in valve 18. The thus further regenerated carrier particles flow over the top end of tube 17 and down annular path 22, discharging in primary cracking zone 15 to contact again the oil treated therein. The gases emerging from interface 30 are separately withdrawn through outlet 24.

In the modified reactor of FIGURE 2, the central tube 17 and its associated elements, shown in FIGURE 1, have been replaced by partition 31 disposed in zone 12 to form the second regeneration zone. The second regeneration zone is connected by duct 32 to a cyclone separator 33 at the top of the reactor. Thus, regenerating gas introduced into the second regenereation zone by way of inlet 34 not only efiects the further gasification of the carbonaceous deposit on the carrier particles which has been partly consumed in the first regeneration zone 12 but also transports the carrier particles up through duct 32 into cyclone 33. There, the gaseous products are separated and with-drawn through outlet 24- while the regenerated canier particles flow down through standpipe 35 into primary cracking zone 15.

The fiowsheet of FIGURE 3 shows that the total gaseous efiluent from outlet 28 of a reactor 10 of the type shown in FIGURE 1 or 2, flows to a recovery plant 40 wherein the efiluent is treated to separate normally gaseous products and heavy oils from the gasoline fraction. The gaseous products leave plant 40' through line 41 and the heavy oils through line 42 while the gasoline fraction passes through line 43 to inlet 44 of hydrotreating reactor 45. Simultaneously, hydrogen-containing product gases Withdrawn from the second regeneration zone of reactor 10 by way of outlet 24 are passed either directly through valved line 26 and line 47 to inlet 44 or through valved line 48 and hydrogen-enriching plant 49 whence a hydrogen-enriched stream flows by way of line 47 to inlet 44. Plant 49 may involve simply an absorption system for removing carbon dioxide from the gases leaving reactor 15) at outlet 24, thus yielding-a stream with a higher concentration of hydrogen. Alternatively, a further increase in the concentration of hydrogen may be obtained by including in plant 49 a water-gas shift converter to convert the carbon monoxide content of the stream to hydrogen and carbon dioxide, the latter being removed by absorption prior to the introduction of the thus treated stream into hydrotreating reactor 45.

FIGURE 3 thus illustrates an important application of the invention wherein not only is a heavy oil converted in reactor 10 to a high yield of gasoline but also the second regeneration zone of reactor 10 produces a gaseous stream containing hydrogen which is well adapted, with or Without further treatment, for use as the gaseous reactant in reactor 45 in treating the gasoline fraction recovered from the operation of reactor 10 to decrease the sulfur content and/ or to improve the storage stability of the finished gasoline product.

In an illustrative operation of this invention, a Boscan (Venezuelan) crude oil having the following charactersitics:

Gravity, degrees API 10.5 Sulfur, weight percent 5 Carbon, Ramsbottom, weight percent 13 is treated in a reactor of the type shown in FIGURE 1. Vessel 10 has an inside diameter of 16 feet and an overall height of 120 feet. Tube 17 has a bottom diameter of 3 /2 feet and increases to a diameter of 4% feet at its top, while tube 21 has an internal diameter of 7 feet. Bauxite is employed as the comminuted contact material being of fiuidizable size range with between 40 and 400 mesh. The total pressure in reactor 10 is maintained at 400 p.s.i.g.; the partial pressure of hydrogen in primary cracking zone 15 is of the order of 100 p.s.i. and is even higher in secondary. cracking zone 16.

Boscan crude oil, preheated to a temperature of 700 F., is introduced through pipe 27 at the rate of 25,000 barrels per day into primary cracking zone 15, and oxygen of by volume purity and steam are introduced through inlet 25 at the rate of 10.5 MM s.c.f.d. (million standard cubic feet per day) and 21 MM s.c.f.-d., respectively, to react in first regeneration zone 12 with the carbonaceous deposit on the bauxite passing into zone 12 from secondary cracking zone 16. The steam-to-oxygen ratio is 2:1.

Additional oxygen of 95% by volume purity and steam are injected through tubular stem 19 and into tube 17 at the respective rates of 5.3 and 13.2 MM s.c.-f.d. The oxygen and steam injected into the bottom of tube 17 effect further gasification of the carbon on the bauxite 7 while transporting the bauxite upwardly through tube 17 at the rate of 360 tons per hour. All of the oxygen is preheated to 300 F. and the steamto 1000" F. The tern- 7 1 Percent L 33 CO 18 CO 19 N 7 1 H O 29 The etiluent removed through outlet 28 contains the volatile products of conversion of the Boscan crude oil admixed with regeneration product gases and excess steam. The following liquid hydrocarbon products are recovered from the efiiuent:

V, Barrels Gasoline (C and higher hydrocarbons up to 400 F.) 10,200 Light gas oil (boiling 400-750 F.) 6,200 Heavy gas oil (boiling above 750 F.) 4,300

The non-condensable portion of the eifiuent, after removing water vapor, contains on a'volume: basis on the order of 25% hydrogen, 25% gaseous hydrocarbons, principally methane, 20% carbon monoxide and 20% carbon dioxide.

In view of the various modifications of the invention which will occur to those skilled in the art upon consideration of the foregoing disclosure without departing from the spirit or scope thereof only such limitations should be imposed as are indicated by the appended claims.

a What is claimed is:

1. The process of converting a heavy hydrocarbon oil of high Rarnsbottom carbon residue which comprises converting said oil at an elevated temperature in a cracking zone in the presence of a hydrogen-containing atmosphere and particulate contact material maintained in a fluidized state, passing said contact material from said cracking zone downwardly to a lower regeneration zone, gasifying in said lower zone a portion of the carbonaceous deposit formed on said contact material during conversion of said oil with steam and high-purityoxygen at a temperature of at least 1600 F. thereby forming regeneration product gases containing hydrogen, flowing said regeneration product gases upwardly through said cracking zone to provide therein a hydrogemcontaining atmosphere as aforesaid, passing said contact material from the lower end portion-of said lower zone to a third zone extending upwardly and substantially coextensive with said cracking and lower zones, gasifying a further portion of said carbonaceousdeposit with an oxygen-containing gas while effecting upward fluidized flow of said contact material in said third zone, withdrawing a gaseous product efiluent fromthe top end portion of said third zone as a separate stream, and passing said contact material from the top end portion of said third zone by gravity flow to said cracking zone.

2. The process of claim 1 wherein said contact material in said third zone is maintained as an up-flow fluidized bed with a gas-solid interface at a level above that of the gas-solid interface in said cracking zone. 3. The process of claim 1 wherein the gasification in said third zone is carried out with high-purity oxygen and steam at an elevated temperature effective for the production of hydrogen.

4. The process of claim 1 wherein a secondary cracking zone is interposed between said cracking and lower zones whereby said contact material from said cracking zone first passes downwardly through said secondary zone while said regeneration product gases from said lower zone first flow upwardly through said secondary zone.

5. The process of claim 4.wherein the temperature in the cracking zone is maintained in the range of 850 to 1100 F., the temperature in the lower zone is maintained in the range of 1700v to 2000 F., and a temperature gradient is maintained in the secondary cracking zone with a temperature at the upper end of said secondary zonerclose to the temperature'in said cracking zone and a temperature at the lower end of said secondary zone close to the temperature in said lower zone.

6. The process of claim 1 wherein the temperature of said contact material is decreased during passage through said third zone.

References Cited in the file of this patent UNITED STATES PATENTS 2,362,270 Hemminger Nov. 7, 1944 2,448,549 Reed et a1 Sept. 7, 1948 2,450,753 Guyer n Oct. 5, 1948 2,506,122 Watson May 2, 1950 2,577,808 Pye Dec. 11, 1951 2,585,238 Gerhold Dec. 12, 1951 2,602,019 Odell July 1, 1952 2,631,921 Odell Mar. 17, 1953 2,661,324 Letter Dec. 1, 1953 2,666,526 Odell Jan. 19, 1954 2,885,344 Garbo May 5, 1959 

1. THE PROCESS OF COVERTING A HEAVY HYDROCARBON OIL OF HIGH RAMSBOTTOM CARBON RESIDUE WHICH COMPRISES CONVERTING SAID OIL AT AN ELEVATED TEMPERATURE IN A CRACKING ZONE IN THE PRESENCE OF A HYDROGEN-CONTAINING ATMOSPHERE AND PARTICULATE CONTACT MATERIAL MAINTAINED IN A FLUIDIZED STATE, PASSING SAID CONTACT MATERIAL FROM SAID CRACKING ZONE DOWNWARDLY TO A LOWER REGENERATION ZONE, GASIFYING IN SAID LOWER ZONE A PORTION OF THE CARBONZCEOUS DEPOSIT FORMED ON SAID CONTACT MATERIAL DURING CONVERSION OF SAID OIL WITH STEAM AND HIGH-PURITY OXYGEEN AT A TEMPERATURE OF AT LEAST 1600*F. THEREBY FORMING REGNERATION PRODUCT GASES CONTAINING HYDROGEEN, FLOWING SAID REGENERATION PRODUCT GASES UPWARDLY THROUGH SAID CRACKING ZONE TO PROVIDDE THEREIN A HYDROGEN-CONTAINING ATMOSPHERE AS AFORESAID, PASSING SAID CONTACT MATERIAL FROM THE LOWER END PORTION OF SAID LOWER ZONE TO A THIRD ZONE EXTEENDING UPWARDLY AND SUBSTANTIALLY COEXTENSIVE WITH SAID CRACKING AND LOWER ZONES, GASIFYING A FURTHER PORTION OF SAID CARBONACEOUS DEPOSIT WITH AN OXYGEEN-CONTAINING GAS WHILE 